An important means for the early diagnosis of carcinoma of the prostate is a rectal examination. Hard areas and palpable nodules are recommended for an examination by biopsy. Carcinoma cells are found to be present in about 50% of all cases with suspect nodules. In these cases, tissue samples obtained by so-called punch biopsy have proved to be particularly useful.
Most urologists long ago discarded the earlier method of obtaining a transrectal punch biopsy by means of a punch-biopsy cannula with an outside diameter of more than 2 mm. The reason was the high incidence of complications due to injury and bleeding in the region of the rectal mucosa, because the cannula's outside diameter was too great and direct digital guidance (in a sterile glove) was essential for penetrating to the region of the intestinal mucosa, prostate, and capsule. Without an aiming device for the punch cannula, the procedure was relatively painful and time-consuming, and could be performed only on in-patients and under general anesthesia.
For outpatient treatment in the urologist's consulting rooms, the only feasible method was the transperineal access for punch biopsy. If outpatient treatment was considered at all, then the preferred method for this was under local anesthesia. However, the great majority of prostate punch biopsies is still performed on in-patients under local or general anesthesia.
The position changed to some extent with the introduction of an instrument for punch biopsy, the so-called biopsy system. This system consists of a punch which houses the complete mechanical system for controlling the procedure for taking a cylindrical tissue sample from the prostate by a punch-biopsy cannula comprising a sleeve-shaped knife and a stylet which slides within the knife. The punch has a spring-loaded control which times the action of the stylet and sleeve-shaped knife to ensure that they shoot out suddenly and in the proper sequence into the tissue, and that the punch and the cutting mechanism work properly.
To obtain a tissue sample, the surgeon guides the cannula from the perineum toward the capsule of the prostate and releases the punch. The time interval between the movement of the mandrin and of the knife is only a few hundredths of a second. When the cannula is released, it shoots out about 23 mm. After the puncture, the cover of the punch can be opened, the biopsy cannula taken out, the stylet moved forward, and the tissue sample in the recess of the stylet removed. The punch can then be cocked again for the next puncture. Reference may be had to U.S. Pat. No. 4,600,014 and BIOPSY-CUT AN AUTOMATIC SYSTEM FOR BIOPSY . . . , Nier Blase Prostata, March 1988, Pages 15-17.
Since the system described above has become commercially available, it has been used increasingly for punch biopsies on outpatients in the urologist's consulting rooms, because it permits a fast punching procedure and provides greater precision for obtaining tissue material of consistently good quality for pathological examination.
Force of habit among urologists and the lack of a suitable aiming system for the punch-biopsy cannula has resulted in continued use of the transperineal access. But this suffers from the disadvantage that, to reach the prostate, the biopsy cannula has to travel relatively far in passing through the perineum, and one can never be certain of striking any specific areas of the prostate with suspicious changes.
A further major disadvantage of this system is the fact that the puncture cannula advances about 23 mm during the biopsy process. This distance is fixed and cannot be adjusted. In patients with a very small prostate, after hormone therapy, or after resection, this puncture depth may be greatly excessive. In such cases, the probe may penetrate beyond the organ and, for example, puncture the bladder, the urethra or a periprostatic venous plexus.